Optimization of ultrasound-assisted extraction of L-ascorbic acid from Adansonia digitata (Linn.) and evaluation of its antityrosinase activity

Background: Adansonia digitata (Linn.) is a widely distributed tree and its edible fruit pulp is well known to have L-ascorbic acid (AA) in high amounts. AA is essential for collagen biosynthesis and has been reported to have antioxidant and skin-lightening properties. Objectives: The aim of this study was to optimize the extraction of AA from the fruit pulp of A. digitata by ultrasound-assisted extraction and to evaluate the antityrosinase activity of the extract. Materials and Methods: A rotatable central composite design was used to investigate the effect of process variables by surface response methodology. The effect of key parameters of extraction temperature (30°C–40°C), extraction time (12–28 min), and ratio solvent to material (7–13 mL/g) was investigated on AA content. Then, mushroom tyrosinase was used to evaluate the antityrosinase activity of the extract. Results: The optimal conditions were obtained with a temperature of 43.4°C, in 23.5 min with a ratio solvent to material of 15.04 mL/g. Under these conditions, AA content from A. digitata (167.4 ± 5.724 mg AA per 100 g dry weight) was determined. Antityrosinase activity of A. digitata extract containing AA was 31.36% ± 1.65%. After degradation of AA, tyrosinase activity decreases to 24.21% ± 1.43%. Conclusion: AA contained in A. digitata extract show to increases significantly the inhibition of enzymatic tyrosinase activity. This extract may have a potential impact on skin depigmentation for the treatment of hyperpigmentation disorders.